diff --git a/Gemfile b/Gemfile
index ed047ed4b0..22a59f1342 100644
--- a/Gemfile
+++ b/Gemfile
@@ -51,6 +51,7 @@ group :development, :test do
   gem "awesome_print"
   gem "guard-rspec"
   gem "pry-rails"
+  gem "pry-nav"
   gem "rspec-rails", "~> 3.8"
   gem "terminal-notifier-guard"
   gem "terminal-notifier"
diff --git a/Gemfile.lock b/Gemfile.lock
index 44a9ffe320..a3b91597dd 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -275,6 +275,8 @@ GEM
     pry (0.12.2)
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
+    pry-nav (0.3.0)
+      pry (>= 0.9.10, < 0.13.0)
     pry-rails (0.3.9)
       pry (>= 0.10.4)
     public_suffix (3.0.3)
@@ -508,6 +510,7 @@ DEPENDENCIES
   paperclip
   pg (~> 1.1.3)
   prawn-rails
+  pry-nav
   pry-rails
   puma
   rails (~> 5.2.2)
diff --git a/app/controllers/adjustments_controller.rb b/app/controllers/adjustments_controller.rb
index 7366ee861e..03398c645a 100644
--- a/app/controllers/adjustments_controller.rb
+++ b/app/controllers/adjustments_controller.rb
@@ -1,7 +1,5 @@
 # Provides limited CRUD for Adjustments, which are the way that Diaper Banks fix incorrect inventory totals at Storage Locations
 class AdjustmentsController < ApplicationController
-  before_action :set_adjustment, only: %i(show destroy)
-
   # GET /adjustments
   # GET /adjustments.json
   def index
@@ -13,44 +11,45 @@ def index
 
   # GET /adjustments/1
   # GET /adjustments/1.json
-  def show; end
+  def show
+    @adjustment = current_organization.adjustments.find(params[:id])
+  end
 
   # GET /adjustments/new
   def new
     @adjustment = current_organization.adjustments.new
     @adjustment.line_items.build
-    @storage_locations = current_organization.storage_locations
-    @items = current_organization.items.alphabetized
+    load_form_collections
   end
 
   # POST /adjustments
   def create
     @adjustment = current_organization.adjustments.new(adjustment_params)
-    @storage_locations = current_organization.storage_locations
-    @items = current_organization.items.alphabetized
-
-    if @adjustment.valid?
-      @adjustment.storage_location.adjust!(@adjustment)
 
-      if @adjustment.save
-        redirect_to adjustment_path(@adjustment), notice: "Adjustment was successfully created."
-      else
-        flash[:error] = @adjustment.errors.collect { |model, message| "#{model}: " + message }.join("<br />".html_safe)
-        render :new
+    if @adjustment.valid? && @adjustment.save
+      increasing_adjustment, decreasing_adjustment = @adjustment.split_difference
+      ActiveRecord::Base.transaction do
+        @adjustment.storage_location.increase_inventory increasing_adjustment
+        @adjustment.storage_location.decrease_inventory decreasing_adjustment
       end
+
+      redirect_to adjustment_path(@adjustment), notice: "Adjustment was successful."
     else
       flash[:error] = @adjustment.errors.collect { |model, message| "#{model}: " + message }.join("<br />".html_safe)
+      load_form_collections
       render :new
     end
   rescue Errors::InsufficientAllotment => ex
     flash[:error] = ex.message
+    load_form_collections
     render :new
   end
 
   private
 
-  def set_adjustment
-    @adjustment = current_organization.adjustments.find(params[:id])
+  def load_form_collections
+    @storage_locations = current_organization.storage_locations
+    @items = current_organization.items.alphabetized
   end
 
   def adjustment_params
diff --git a/app/controllers/audits_controller.rb b/app/controllers/audits_controller.rb
index 22f8826d2e..252b3f1f9c 100644
--- a/app/controllers/audits_controller.rb
+++ b/app/controllers/audits_controller.rb
@@ -34,7 +34,11 @@ def finalize
       end
     end
 
-    @audit.adjustment.storage_location.adjust!(@audit.adjustment)
+    increasing_adjustment, decreasing_adjustment = @audit.adjustment.split_difference
+    ActiveRecord::Base.transaction do
+      @audit.storage_location.increase_inventory increasing_adjustment
+      @audit.storage_location.decrease_inventory decreasing_adjustment
+    end
     @audit.finalized!
     redirect_to audit_path(@audit), notice: "Audit is Finalized."
   end
diff --git a/app/controllers/distributions_controller.rb b/app/controllers/distributions_controller.rb
index fc65dfbcfd..854c632b9d 100644
--- a/app/controllers/distributions_controller.rb
+++ b/app/controllers/distributions_controller.rb
@@ -19,16 +19,14 @@ def print
     end
   end
 
-  # TODO: This should be renamed :destroy, because that's what it does. I think the name is vestigial from a time when it didn't actually destroy the object
-  def reclaim
+  def destroy
     ActiveRecord::Base.transaction do
-      @distribution_id = params[:id]
-      distribution = Distribution.find(params[:id])
-      distribution.storage_location.reclaim!(distribution)
+      distribution = current_organization.distributions.find(params[:id])
+      distribution.storage_location.increase_inventory(distribution)
       distribution.destroy!
     end
 
-    flash[:notice] = "Distribution #{@distribution_id} has been reclaimed!"
+    flash[:notice] = "Distribution #{params[:id]} has been reclaimed!"
     redirect_to distributions_path
   end
 
@@ -44,31 +42,25 @@ def index
 
   def create
     @distribution = Distribution.new(distribution_params.merge(organization: current_organization))
+    @storage_locations = current_organization.storage_locations
 
     if @distribution.valid?
-      if params[:commit] == "Preview Distribution"
-        @distribution.line_items.combine!
-        @line_items = @distribution.line_items
-        render :show
+      @distribution.storage_location.decrease_inventory @distribution
+
+      if @distribution.save
+        update_request(params[:distribution][:request_attributes], @distribution.id)
+
+        send_notification(current_organization, @distribution)
+        flash[:notice] = "Distribution created!"
+        session[:created_distribution_id] = @distribution.id
+        redirect_to distributions_path
       else
-        @distribution.storage_location.distribute!(@distribution)
-
-        if @distribution.save
-          update_request(params[:distribution][:request_attributes], @distribution.id)
-
-          send_notification(current_organization.id, @distribution.id)
-          flash[:notice] = "Distribution created!"
-          session[:created_distribution_id] = @distribution.id
-          redirect_to distributions_path
-        else
-          flash[:error] = "There was an error, try again?"
-          render :new
-        end
+        flash[:error] = "There was an error, try again?"
+        render :new
       end
     else
-      @storage_locations = current_organization.storage_locations
       flash[:error] = "An error occurred, try again?"
-      logger.error "failed to save distribution: #{@distribution.errors.full_messages}"
+      logger.error "[!] DistributionsController#create failed to save distribution: #{@distribution.errors.full_messages}"
       render :new
     end
   rescue Errors::InsufficientAllotment => ex
@@ -109,7 +101,7 @@ def update
     # see examples: https://stackoverflow.com/questions/13605598/how-to-get-a-date-from-date-select-or-select-date-in-rails
     old_issued_at = distribution.issued_at
 
-    if distribution.storage_location.update_distribution!(distribution, distribution_params)
+    if distribution.replace_distribution!(distribution_params)
       @distribution = Distribution.includes(:line_items).includes(:storage_location).find(params[:id])
       @line_items = @distribution.line_items
 
diff --git a/app/controllers/donations_controller.rb b/app/controllers/donations_controller.rb
index f86616a191..676d41cad2 100644
--- a/app/controllers/donations_controller.rb
+++ b/app/controllers/donations_controller.rb
@@ -41,20 +41,20 @@ def scale_intake
                                 line_items_attributes: { "0" => { "item_id" => params["diaper_type"],
                                                                   "quantity" => params["number_of_diapers"],
                                                                   "_destroy" => "false" } })
-    @donation.storage_location.intake! @donation
+    @donation.storage_location.increase_inventory @donation
     render status: :ok, json: @donation.to_json
   end
 
   def create
-    @donation = Donation.new(donation_params.merge(organization: current_organization))
+    @donation = current_organization.donations.new(donation_params)
     if @donation.save
-      @donation.storage_location.intake! @donation
+      @donation.storage_location.increase_inventory @donation
       redirect_to donations_path
     else
       load_form_collections
       @donation.line_items.build if @donation.line_items.count.zero?
       flash[:error] = "There was an error starting this donation, try again?"
-      Rails.logger.error "ERROR: #{@donation.errors}"
+      Rails.logger.error "[!] DonationsController#create Error: #{@donation.errors}"
       render action: :new
     end
   end
@@ -78,9 +78,7 @@ def show
 
   def update
     @donation = Donation.find(params[:id])
-    previous_quantities = @donation.line_items_quantities
-    if @donation.update(donation_params)
-      @donation.storage_location.adjust_from_past!(@donation, previous_quantities)
+    if @donation.replace_increase!(donation_params)
       redirect_to donations_path
     else
       render "edit"
@@ -88,8 +86,13 @@ def update
   end
 
   def destroy
-    @donation = current_organization.donations.includes(:line_items, storage_location: :inventory_items).find(params[:id])
-    @donation.destroy
+    ActiveRecord::Base.transaction do
+      donation = current_organization.donations.find(params[:id])
+      donation.storage_location.decrease_inventory(donation)
+      donation.destroy!
+    end
+
+    flash[:notice] = "Donation #{params[:id]} has been removed!"
     redirect_to donations_path
   end
 
diff --git a/app/controllers/purchases_controller.rb b/app/controllers/purchases_controller.rb
index 615e786716..2acb5b8831 100644
--- a/app/controllers/purchases_controller.rb
+++ b/app/controllers/purchases_controller.rb
@@ -20,13 +20,13 @@ def index
   def create
     @purchase = current_organization.purchases.new(purchase_params)
     if @purchase.save
-      @purchase.storage_location.intake! @purchase
+      @purchase.storage_location.increase_inventory @purchase
       redirect_to purchases_path
     else
       load_form_collections
       @purchase.line_items.build if @purchase.line_items.count.zero?
       flash[:error] = "There was an error starting this purchase, try again?"
-      Rails.logger.error "ERROR: #{@purchase.errors}"
+      Rails.logger.error "[!] PurchasesController#create ERROR: #{@purchase.errors}"
       render action: :new
     end
   end
@@ -50,10 +50,7 @@ def show
 
   def update
     @purchase = current_organization.purchases.find(params[:id])
-    @purchase.changed?
-    previous_quantities = @purchase.line_items_quantities
-    if @purchase.update(purchase_params)
-      @purchase.storage_location.adjust_from_past!(@purchase, previous_quantities)
+    if @purchase.replace_increase!(purchase_params)
       redirect_to purchases_path
     else
       render "edit"
@@ -61,8 +58,13 @@ def update
   end
 
   def destroy
-    @purchase = current_organization.purchases.includes(:line_items, storage_location: :inventory_items).find(params[:id])
-    @purchase.destroy
+    ActiveRecord::Base.transaction do
+      purchase = current_organization.purchases.find(params[:id])
+      purchase.storage_location.decrease_inventory(purchase)
+      purchase.destroy!
+    end
+
+    flash[:notice] = "Purchase #{params[:id]} has been removed!"
     redirect_to purchases_path
   end
 
diff --git a/app/controllers/transfers_controller.rb b/app/controllers/transfers_controller.rb
index 66750acc2d..bc2f843fc5 100644
--- a/app/controllers/transfers_controller.rb
+++ b/app/controllers/transfers_controller.rb
@@ -12,25 +12,22 @@ def create
     @transfer = current_organization.transfers.new(transfer_params)
 
     if @transfer.valid?
-      @transfer.from.move_inventory!(@transfer)
-
-      if @transfer.save
-        redirect_to transfers_path, notice: "Transfer was successfully created."
-      else
-        flash[:error] = "There was an error, try again?"
-        render :new
+      ActiveRecord::Base.transaction do
+        @transfer.save
+        @transfer.from.decrease_inventory @transfer
+        @transfer.to.increase_inventory @transfer
       end
+
+      redirect_to transfers_path, notice: "#{@transfer.line_items.total} items have been transferred from #{@transfer.from.name} to #{@transfer.to.name}!"
     else
       flash[:error] = "There was an error creating the transfer"
-      @storage_locations = current_organization.storage_locations.alphabetized
-      @items = current_organization.items.alphabetized
+      load_form_collections
       @transfer.line_items.build if @transfer.line_items.empty?
       render :new
     end
   rescue Errors::InsufficientAllotment => ex
     flash[:error] = ex.message
-    @storage_locations = current_organization.storage_locations.alphabetized
-    @items = current_organization.items.alphabetized
+    load_form_collections
     @transfer.line_items.build if @transfer.line_items.empty?
     render :new
   end
@@ -38,8 +35,7 @@ def create
   def new
     @transfer = current_organization.transfers.new
     @transfer.line_items.build
-    @storage_locations = current_organization.storage_locations.alphabetized
-    @items = current_organization.items.alphabetized
+    load_form_collections
   end
 
   def show
@@ -50,6 +46,11 @@ def show
 
   private
 
+  def load_form_collections
+    @storage_locations = current_organization.storage_locations.alphabetized
+    @items = current_organization.items.alphabetized
+  end
+
   def transfer_params
     params.require(:transfer).permit(:from_id, :to_id, :comment,
                                      line_items_attributes: %i(item_id quantity _destroy))
diff --git a/app/models/adjustment.rb b/app/models/adjustment.rb
index d19f411e93..9169b66e69 100644
--- a/app/models/adjustment.rb
+++ b/app/models/adjustment.rb
@@ -30,6 +30,14 @@ def self.storage_locations_adjusted_for(organization)
     includes(:storage_location).where(organization_id: organization.id).collect(&:storage_location)
   end
 
+  def split_difference
+    pre_adjustment = line_items.partition { |line_item| line_item.quantity.positive? }
+    increasing_adjustment, decreasing_adjustment = pre_adjustment.map { |adjustment| Adjustment.new(line_items: adjustment) }
+
+    decreasing_adjustment.line_items.each { |line_item| line_item.quantity *= -1 }
+    [increasing_adjustment, decreasing_adjustment]
+  end
+
   def self.csv_export_headers
     ["Created", "Organization", "Storage Location", "Comment", "Changes"]
   end
diff --git a/app/models/concerns/itemizable.rb b/app/models/concerns/itemizable.rb
index e40f67012d..63bd29853c 100644
--- a/app/models/concerns/itemizable.rb
+++ b/app/models/concerns/itemizable.rb
@@ -21,11 +21,11 @@ def combine!
         # First we'll collect all the line_items that are used
         combined = {}
         parent_id = first.itemizable_id
-        each do |i|
-          next unless i.valid?
+        each do |line_item|
+          next unless line_item.valid?
 
-          combined[i.item_id] ||= 0
-          combined[i.item_id] += i.quantity
+          combined[line_item.item_id] ||= 0
+          combined[line_item.item_id] += line_item.quantity
         end
         # Delete all the existing ones in this association -- this
         # method aliases to `delete_all`
@@ -67,19 +67,25 @@ def total
     validates_associated :line_items
   end
 
-  def line_items_quantities
-    line_items.inject(Hash.new) do |hash, line_item|
-      hash[line_item.id] = OpenStruct.new(quantity: line_item.quantity, item_id: line_item.item_id)
-      hash
-    end
-  end
-
   def value_per_itemizable
     line_items.sum(&:value_per_line_item)
   end
 
+  def to_a
+    line_items.map do |l|
+      # When the item isn't found, it's probably just inactive. This ensures it's available.
+      item = Item.unscoped.find(l.item_id)
+      { item_id: item.id, name: item.name, quantity: l.quantity, active: item.active }.with_indifferent_access
+    end
+  end
+
   private
 
+  # From Controller parameters
+  def line_items_attributes(params)
+    Array.wrap(params[:line_items_attributes]&.values)
+  end
+
   def line_item_items_quantity_is_positive
     return if storage_location.nil?
 
diff --git a/app/models/distribution.rb b/app/models/distribution.rb
index 5e42bf0330..e8531b7bcb 100644
--- a/app/models/distribution.rb
+++ b/app/models/distribution.rb
@@ -49,6 +49,26 @@ class Distribution < ApplicationRecord
 
   delegate :name, to: :partner, prefix: true
 
+  # TODO: kill me
+  def replace_distribution!(new_distribution_params)
+    ActiveRecord::Base.transaction do
+      # fixed_distribution_params = new_distribution_params["line_items_attributes"].to_h.values.reject { |f| f["item_id"].blank? && f["quantity"].blank? }
+      # Roll back distribution output by increasing storage location
+      storage_location.increase_inventory(to_a)
+      # Delete the line items -- they'll be replaced later
+      line_items.each(&:destroy!)
+      reload
+
+      # Replace the current distribution with the new parameters
+      update! new_distribution_params
+
+      # Apply the new changes to the storage location inventory
+      storage_location.decrease_inventory(to_a)
+    end
+  rescue ActiveRecord::RecordInvalid
+    false
+  end
+
   def distributed_at
     if is_midnight(issued_at)
       issued_at.to_s(:distribution_date)
diff --git a/app/models/donation.rb b/app/models/donation.rb
index 8ee2e37178..86bffaffaa 100644
--- a/app/models/donation.rb
+++ b/app/models/donation.rb
@@ -43,7 +43,6 @@ class Donation < ApplicationRecord
   }
 
   before_create :combine_duplicates
-  before_destroy :remove_inventory
 
   validates :donation_site, presence:
     { message: "must be specified since you chose '#{SOURCES[:donation_site]}'" },
@@ -91,16 +90,25 @@ def self.daily_quantities_by_source(start, stop)
                       .sum("line_items.quantity")
   end
 
-  # def self.total_received
-  #    self.includes(:line_items).map(&:total_quantity).reduce(0, :+)
-  #  end
-
-  def track(item, quantity)
-    if contains_item_id?(item.id)
-      update_quantity(quantity, item)
-    else
-      LineItem.create(itemizable: self, item_id: item.id, quantity: quantity)
+  def replace_increase!(new_donation_params)
+    old_data = to_a
+    item_ids = line_items_attributes(new_donation_params).map { |i| i[:item_id].to_i }
+
+    ActiveRecord::Base.transaction do
+      line_items.map(&:destroy!)
+      reload
+      Item.reactivate(item_ids)
+      line_items_attributes(new_donation_params).map { |i| i.delete(:id) }
+      update! new_donation_params
+      # Roll back distribution output by increasing storage location
+      storage_location.increase_inventory(to_a)
+      # Apply the new changes to the storage location inventory
+      storage_location.decrease_inventory(old_data)
+      # TODO: Discuss this -- *should* we be removing InventoryItems when they hit 0 count?
+      storage_location.inventory_items.where(quantity: 0).destroy_all
     end
+  rescue ActiveRecord::RecordInvalid
+    false
   end
 
   def remove(item)
@@ -122,24 +130,6 @@ def total_quantity
     line_items.sum(:quantity)
   end
 
-  def contains_item_id?(id)
-    line_items.find_by(item_id: id).present?
-  end
-
-  # Use a negative quantity to subtract inventory
-  def update_quantity(quantity, item)
-    item_id = item.to_i
-    line_item = line_items.find_by(item_id: item_id)
-    line_item.quantity += quantity
-    # Inventory can never be negative
-    line_item.quantity = 0 if line_item.quantity.negative?
-    line_item.save
-  end
-
-  def remove_inventory
-    storage_location.remove!(self)
-  end
-
   def self.csv_export_headers
     ["Source", "Date", "Donation Site", "Storage Location", "Quantity of Items", "Variety of Items"]
   end
diff --git a/app/models/item.rb b/app/models/item.rb
index 4a2f0093e9..35e45822d9 100644
--- a/app/models/item.rb
+++ b/app/models/item.rb
@@ -56,6 +56,11 @@ def self.barcodes_for(item)
     BarcodeItem.where("barcodeable_id = ?", item.id)
   end
 
+  def self.reactivate(item_ids)
+    item_ids = Array.wrap(item_ids)
+    Item.unscoped.where(id: item_ids).find_each { |item| item.update(active: true) }
+  end
+
   # Override `destroy` to ensure Item isn't accidentally destroyed
   # without first being disassociated with its historical presence
   def destroy
diff --git a/app/models/purchase.rb b/app/models/purchase.rb
index e32ed917d5..1bf34b0b20 100644
--- a/app/models/purchase.rb
+++ b/app/models/purchase.rb
@@ -39,7 +39,6 @@ class Purchase < ApplicationRecord
   }
 
   before_create :combine_duplicates
-  before_destroy :remove_inventory
 
   validates :amount_spent, numericality: { greater_than: 0 }
 
@@ -51,22 +50,6 @@ def purchased_from_view
     vendor.nil? ? purchased_from : vendor.business_name
   end
 
-  def remove_inventory
-    storage_location.remove!(self)
-  end
-
-  def track(item, quantity)
-    if contains_item_id?(item.id)
-      update_quantity(quantity, item)
-    else
-      LineItem.create(itemizable: self, item_id: item.id, quantity: quantity)
-    end
-  end
-
-  def contains_item_id?(id)
-    line_items.find_by(item_id: id).present?
-  end
-
   def total_quantity
     line_items.sum(:quantity)
   end
@@ -78,14 +61,26 @@ def remove(item)
     line_item&.destroy
   end
 
-  # Use a negative quantity to subtract inventory
-  def update_quantity(quantity, item)
-    item_id = item.to_i
-    line_item = line_items.find_by(item_id: item_id)
-    line_item.quantity += quantity
-    # Inventory can never be negative
-    line_item.quantity = 0 if line_item.quantity.negative?
-    line_item.save
+  def replace_increase!(new_purchase_params)
+    old_data = to_a
+    item_ids = line_items_attributes(new_purchase_params).map { |i| i[:item_id].to_i }
+
+    ActiveRecord::Base.transaction do
+      line_items.map(&:destroy!)
+      reload
+      Item.reactivate(item_ids)
+      line_items_attributes(new_purchase_params).map { |i| i.delete(:id) }
+
+      update! new_purchase_params
+      # Roll back distribution output by increasing storage location
+      storage_location.increase_inventory(to_a)
+      # Apply the new changes to the storage location inventory
+      storage_location.decrease_inventory(old_data)
+      # TODO: Discuss this -- *should* we be removing InventoryItems when they hit 0 count?
+      storage_location.inventory_items.where(quantity: 0).destroy_all
+    end
+  rescue ActiveRecord::RecordInvalid
+    false
   end
 
   def self.csv_export_headers
@@ -105,7 +100,7 @@ def csv_export_attributes
   private
 
   def combine_duplicates
-    Rails.logger.info "Combining!"
+    Rails.logger.info "[!] Purchase.combine_duplicates: Combining!"
     line_items.combine!
   end
 end
diff --git a/app/models/storage_location.rb b/app/models/storage_location.rb
index 08e36bbb13..86300596cd 100644
--- a/app/models/storage_location.rb
+++ b/app/models/storage_location.rb
@@ -71,89 +71,7 @@ def to_csv
     end
   end
 
-  def intake!(adjustment)
-    log = {}
-    adjustment.line_items.each do |line_item|
-      inventory_item = InventoryItem.find_or_create_by(storage_location_id: id,
-                                                       item_id: line_item.item_id) do |inv_item|
-        inv_item.quantity = 0
-      end
-      inventory_item.quantity += begin
-                                   line_item.quantity
-                                 rescue StandardError
-                                   0
-                                 end
-      inventory_item.save
-      log[line_item.item_id] = "+#{line_item.quantity}"
-    end
-    log
-  end
-
-  def remove!(donation_or_purchase)
-    log = {}
-    donation_or_purchase.line_items.each do |line_item|
-      inventory_item = InventoryItem.find_by(storage_location: id, item_id: line_item.item_id)
-      if (inventory_item.quantity - line_item.quantity) <= 0
-        inventory_item.destroy
-      else
-        inventory_item.update(quantity: inventory_item.quantity - line_item.quantity)
-      end
-      log[line_item.item_id] = "-#{line_item.quantity}"
-    end
-    log
-  end
-
-  def adjust_from_past!(donation_or_purchase, previous_line_item_values)
-    donation_or_purchase.line_items.each do |line_item|
-      inventory_item = InventoryItem.find_or_create_by(storage_location_id: id, item_id: line_item.item_id)
-      # If the item wasn't deleted by the user, then it will be present to be deleted
-      # here, and delete returns the item as a return value.
-      if previous_line_item_value = previous_line_item_values.delete(line_item.id)
-        inventory_item.quantity += line_item.quantity
-        inventory_item.quantity -= previous_line_item_value.quantity
-        inventory_item.save!
-      end
-      inventory_item.destroy! if inventory_item.quantity.zero?
-    end
-    # Update storage for line items that are no longer persisted because they
-    # were removed durring the updated/delete process.
-    previous_line_item_values.values.each do |value|
-      inventory_item = InventoryItem.find_or_create_by(storage_location_id: id, item_id: value.item_id)
-      inventory_item.decrement!(:quantity, value.quantity)
-      inventory_item.destroy! if inventory_item.quantity.zero?
-    end
-  end
-
-  def distribute!(distribution)
-    updated_quantities = {}
-    insufficient_items = []
-    distribution.line_items.each do |line_item|
-      inventory_item = inventory_items.find_by(item: line_item.item)
-      next if inventory_item.nil?
-
-      if inventory_item.quantity >= line_item.quantity
-        updated_quantities[inventory_item.id] = (updated_quantities[inventory_item.id] ||
-                                                 inventory_item.quantity) - line_item.quantity
-      else
-        insufficient_items << {
-          item_id: line_item.item.id,
-          item_name: line_item.item.name,
-          quantity_on_hand: inventory_item.quantity,
-          quantity_requested: line_item.quantity
-        }
-      end
-    end
-
-    unless insufficient_items.empty?
-      raise Errors::InsufficientAllotment.new(
-        "Distribution line_items exceed the available inventory",
-        insufficient_items
-      )
-    end
-
-    update_inventory_inventory_items(updated_quantities)
-  end
-
+  # NOTE: We should generalize this elsewhere -- Importable concern?
   def self.import_csv(csv, organization)
     csv.each do |row|
       loc = StorageLocation.new(row.to_hash)
@@ -162,105 +80,91 @@ def self.import_csv(csv, organization)
     end
   end
 
+  # NOTE: We should generalize this elsewhere -- Importable concern?
   def self.import_inventory(filename, org, loc)
     current_org = Organization.find(org)
     adjustment = current_org.adjustments.create(storage_location_id: loc.to_i, comment: "Starting Inventory")
-    CSV.parse(filename, headers: false) do |row|
+    # NOTE: this was originally headers: false; it may create buggy behavior
+    CSV.parse(filename, headers: true) do |row|
       adjustment.line_items
                 .create(quantity: row[0].to_i, item_id: current_org.items.find_by(name: row[1]))
     end
-    adjustment.storage_location.intake!(adjustment)
+    adjustment.storage_location.increase_inventory(adjustment)
   end
 
-  # Used to move inventory between StorageLocations; reflects items being physically moved
-  # Ex: move 500 size "2" diapers from main warehouse to overflow warehouse because insufficient space in main warehouse
-  def move_inventory!(transfer)
-    updated_quantities = {}
-    item_validator = Errors::InsufficientAllotment.new("Transfer items exceeds \
-                                                        the available inventory")
-    transfer.line_items.each do |line_item|
-      inventory_item = inventory_items.find_by(item: line_item.item)
-      new_inventory_item = transfer.to.inventory_items.find_or_create_by(item: line_item.item)
-      next if inventory_item.nil? || inventory_item.quantity.zero?
+  # FIXME: After this is stable, revisit how we do logging
+  def increase_inventory(itemizable_array)
+    itemizable_array = itemizable_array.to_a
 
-      if inventory_item.quantity >= line_item.quantity
-        updated_quantities[inventory_item.id] = (updated_quantities[inventory_item.id] ||
-                                                 inventory_item.quantity) - line_item.quantity
-        updated_quantities[new_inventory_item.id] = (updated_quantities[new_inventory_item.id] ||
-          new_inventory_item.quantity) + line_item.quantity
-      else
-        item_validator.add_insufficiency(line_item.item,
-                                         inventory_item.quantity,
-                                         line_item.quantity)
-      end
+    # This is, at least for now, how we log changes to the inventory made in this call
+    log = {}
+    # Iterate through each of the line-items in the moving box
+    Item.reactivate(itemizable_array.map { |item_hash| item_hash[:item_id] })
+    itemizable_array.each do |item_hash|
+      # Locate the storage box for the item, or create a new storage box for it
+      inventory_item = inventory_items.find_or_create_by!(item_id: item_hash[:item_id])
+      # Increase the quantity-on-record for that item
+      inventory_item.increment!(:quantity, item_hash[:quantity].to_i)
+      # Record in the log that this has occurred
+      log[item_hash[:item_id]] = "+#{item_hash[:quantity]}"
     end
-
-    raise item_validator unless item_validator.satisfied?
-
-    update_inventory_inventory_items(updated_quantities)
+    # log could be pulled from dirty AR stuff?
+    # Save the final changes -- does this need to occur here?
+    save
+    # return log
+    log
   end
 
-  # Used to adjust inventory at a StorageLocation to reflect reality
-  # Ex: we thought we had 200 size "5" diapers, but we actually have 180 size "5" diapers
-  def adjust!(adjustment)
-    updated_quantities = {}
-    item_validator = Errors::InsufficientAllotment.new("Adjustment exceeds the available inventory")
+  # TODO: re-evaluate this for optimization
+  def decrease_inventory(itemizable_array)
+    itemizable_array = itemizable_array.to_a
 
-    adjustment.line_items.each do |line_item|
-      inventory_item = inventory_items.find_by(item: line_item.item)
-      next if inventory_item.nil? || inventory_item.quantity.zero?
-
-      if (inventory_item.quantity + line_item.quantity) >= 0
-        updated_quantities[inventory_item.id] = (updated_quantities[inventory_item.id] ||
-                                                 inventory_item.quantity) + line_item.quantity
-      else
-        item_validator.add_insufficiency(line_item.item,
-                                         inventory_item.quantity,
-                                         line_item.quantity)
-      end
+    # This is, at least for now, how we log changes to the inventory made in this call
+    log = {}
+    # This tracks items that have insufficient inventory counts to be reduced as much
+    insufficient_items = []
+    # Iterate through each of the line-items in the moving box
+    itemizable_array.each do |item_hash|
+      # Locate the storage box for the item, or create an empty storage box
+      inventory_item = inventory_items.find_by(item_id: item_hash[:item_id]) || inventory_items.build
+      # If we've got sufficient inventory in the storage box to fill the moving box, then continue
+      next unless inventory_item.quantity < item_hash[:quantity]
+
+      # Otherwise, we need to record that there was insufficient inventory on-hand
+      insufficient_items << {
+        item_id: item_hash[:item_id],
+        item_name: item_hash[:name],
+        quantity_on_hand: inventory_item.quantity,
+        quantity_requested: item_hash[:quantity]
+      }
     end
 
-    raise item_validator unless item_validator.satisfied?
-
-    update_inventory_inventory_items(updated_quantities)
-  end
-
-  def reclaim!(distribution)
-    ActiveRecord::Base.transaction do
-      distribution.line_items.each do |line_item|
-        if line_item.item.nil? || !line_item.item.active?
-          Item.unscoped.find(line_item.item_id).update(active: true)
-          line_item.reload
-        end
-        inventory_item = inventory_items.find_by(item: line_item.item)
-        inventory_item.update!(quantity: inventory_item.quantity + line_item.quantity)
-      end
+    # NOTE: Could this be handled by a validation instead?
+    # If we found any insufficiencies
+    unless insufficient_items.empty?
+      # Raise this custom error with information about each of the items that showed insufficient
+      # This bails out of the method!
+      raise Errors::InsufficientAllotment.new(
+        "Requested items exceed the available inventory",
+        insufficient_items
+      )
     end
-  end
-
-  def update_distribution!(distribution, new_distribution_params)
-    ActiveRecord::Base.transaction do
-      distribution.line_items.each do |line_item|
-        inventory_item = inventory_items.find_or_create_by!(item: line_item.item)
-        inventory_item.update!(quantity: (inventory_item.quantity || 0) + line_item.quantity)
-        line_item.destroy!
-      end
-      distribution = distribution.reload
-      distribution.update! new_distribution_params
-
-      distribution.line_items.each do |line_item|
-        inventory_item = inventory_items.find_by(item: line_item.item)
-        raise ActiveRecord::Rollback, "Failed to update distribution, please contact tech support if this problem persists" if inventory_item.nil?
 
-        if inventory_item.quantity == line_item.quantity # otherwise this would make the quantity 0 and an exception would be thrown
-          inventory_item.destroy!
-        else
-          inventory_item.update!(quantity: inventory_item.quantity - line_item.quantity)
-        end
-      end
+    # Re-run through the items in the moving box again
+    itemizable_array.each do |item_hash|
+      # Look for the moving box for this item -- we know there is sufficient quantity this time
+      # Raise AR:RNF if it fails to find it -- though that seems moot since it would have been
+      # captured by the previous block.
+      inventory_item = inventory_items.find_by(item_id: item_hash[:item_id])
+      # Reduce the inventory box quantity
+      inventory_item.decrement!(:quantity, item_hash[:quantity])
+      # Record in the log that this has occurred
+      log[item_hash[:item_id]] = "-#{item_hash[:quantity]}"
     end
-  rescue ActiveRecord::RecordInvalid
-    false
+    # log could be pulled from dirty AR stuff
+    save!
+    # return log
+    log
   end
 
   def self.csv_export_headers
@@ -270,14 +174,4 @@ def self.csv_export_headers
   def csv_export_attributes
     [name, address, size]
   end
-
-  private
-
-  def update_inventory_inventory_items(records)
-    ActiveRecord::Base.transaction do
-      records.each do |inventory_item_id, quantity|
-        InventoryItem.find(inventory_item_id).update(quantity: quantity)
-      end
-    end
-  end
 end
diff --git a/app/views/distributions/_distribution_row.html.erb b/app/views/distributions/_distribution_row.html.erb
index 8f8de5e015..1a9b46e868 100644
--- a/app/views/distributions/_distribution_row.html.erb
+++ b/app/views/distributions/_distribution_row.html.erb
@@ -8,10 +8,9 @@
     <%= view_button_to distribution_path(distribution_row) %>
     <%= edit_button_to edit_distribution_path(distribution_row) %>
     <%= print_button_to print_distribution_path(distribution_row, format: :pdf) %>
-    <%= delete_button_to reclaim_distribution_path(distribution_row),
+    <%= delete_button_to distribution_path(distribution_row),
           { confirm: "Are you sure you want to reclaim this distribution to #{distribution_row.partner.name}?",
             text: "Reclaim",
-            method: "post",
             icon: "undo" } 
     %>
   </td>
diff --git a/config/routes.rb b/config/routes.rb
index e0764daac5..b2d4a56a53 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -69,9 +69,8 @@
       end
     end
 
-    resources :distributions, except: %i(destroy) do
+    resources :distributions do
       get :print, on: :member
-      post :reclaim, on: :member
       collection do
         get :pick_ups
       end
diff --git a/spec/controllers/donations_controller_spec.rb b/spec/controllers/donations_controller_spec.rb
index b65931911d..a1c16d43ea 100644
--- a/spec/controllers/donations_controller_spec.rb
+++ b/spec/controllers/donations_controller_spec.rb
@@ -4,6 +4,7 @@
   end
 
   context "While signed in >" do
+    let(:donation) { create(:donation, organization: @organization) }
     before do
       sign_in(@user)
     end
@@ -105,21 +106,21 @@
     end
 
     describe "GET #edit" do
-      subject { get :edit, params: default_params.merge(id: create(:donation)) }
+      subject { get :edit, params: default_params.merge(id: donation.id) }
       it "returns http success" do
         expect(subject).to be_successful
       end
     end
 
     describe "GET #show" do
-      subject { get :show, params: default_params.merge(id: create(:donation, organization: @organization)) }
+      subject { get :show, params: default_params.merge(id: donation.id) }
       it "returns http success" do
         expect(subject).to be_successful
       end
     end
 
     describe "DELETE #destroy" do
-      subject { delete :destroy, params: default_params.merge(id: create(:donation, organization: @organization)) }
+      subject { delete :destroy, params: default_params.merge(id: donation.id) }
       it "redirects to the index" do
         expect(subject).to redirect_to(donations_path)
       end
diff --git a/spec/controllers/purchases_controller_spec.rb b/spec/controllers/purchases_controller_spec.rb
index e749061210..fbf9c87485 100644
--- a/spec/controllers/purchases_controller_spec.rb
+++ b/spec/controllers/purchases_controller_spec.rb
@@ -55,20 +55,20 @@
       end
 
       it "updates storage quantity correctly" do
-        purchase = create(:purchase, :with_items, item_quantity: 10)
+        purchase = create(:purchase, :with_items, item_quantity: 5)
         line_item = purchase.line_items.first
         line_item_params = {
           "0" => {
             "_destroy" => "false",
             item_id: line_item.item_id,
-            quantity: "5",
+            quantity: "10",
             id: line_item.id
           }
         }
         purchase_params = { source: "Purchase Site", line_items_attributes: line_item_params }
         expect do
           put :update, params: default_params.merge(id: purchase.id, purchase: purchase_params)
-        end.to change { purchase.storage_location.inventory_items.first.quantity }.by(-5)
+        end.to change { purchase.storage_location.inventory_items.first.quantity }.by(5)
       end
 
       describe "when removing a line item" do
diff --git a/spec/factories/adjustments.rb b/spec/factories/adjustments.rb
index c5b2c62558..9af6865d6e 100644
--- a/spec/factories/adjustments.rb
+++ b/spec/factories/adjustments.rb
@@ -13,26 +13,19 @@
 FactoryBot.define do
   factory :adjustment do
     organization { Organization.try(:first) || create(:organization) }
-    storage_location { nil }
+    storage_location
     comment { "A comment" }
 
-    after(:build) do |instance, evaluator|
-      instance.storage_location = evaluator.storage_location || create(:storage_location, organization: instance.organization)
-    end
-
     trait :with_items do
+      storage_location { create :storage_location, :with_items, item: item || create(:item), organization: organization }
+
       transient do
         item_quantity { 100 }
         item { nil }
       end
 
       after(:build) do |instance, evaluator|
-        instance.storage_location ||= create(:storage_location, :with_items, item: evaluator.item, organization: instance.organization)
-        item = if evaluator.item.nil?
-                 instance.storage_location.inventory_items.first.item
-               else
-                 evaluator.item
-               end
+        item = evaluator.item || instance.storage_location.inventory_items.first.item
         instance.line_items << build(:line_item, quantity: evaluator.item_quantity, item: item)
       end
     end
diff --git a/spec/features/adjustment_spec.rb b/spec/features/adjustment_spec.rb
index 8edd3ac5c0..832f9ca0ad 100644
--- a/spec/features/adjustment_spec.rb
+++ b/spec/features/adjustment_spec.rb
@@ -17,7 +17,7 @@
     expect do
       click_button "Save"
     end.to change { storage_location.size }.by(add_quantity)
-    expect(page).to have_content("Adjustment was successfully created")
+    expect(page).to have_content("Adjustment was successful")
   end
 
   scenario "User can subtract an inventory adjustment at a storage location", js: true do
@@ -33,7 +33,23 @@
     expect do
       click_button "Save"
     end.to change { storage_location.size }.by(sub_quantity)
-    expect(page).to have_content("Adjustment was successfully created")
+    expect(page).to have_content("Adjustment was successful")
+  end
+
+  scenario "User is informed politely that they're adjusting way too hard", js: true do
+    sub_quantity = -9001
+    storage_location = create(:storage_location, :with_items, item_quantity: 10, organization: @organization)
+    visit url_prefix + "/adjustments"
+    click_on "New Adjustment"
+    select storage_location.name, from: "From storage location"
+    fill_in "Comment", with: "something"
+    select Item.last.name, from: "adjustment_line_items_attributes_0_item_id"
+    fill_in "adjustment_line_items_attributes_0_quantity", with: sub_quantity.to_s
+
+    expect do
+      click_button "Save"
+    end.not_to change { storage_location.size }
+    expect(page).to have_content("items exceed the available inventory")
   end
 
   scenario "User can filter the #index by storage location" do
@@ -48,4 +64,4 @@
 
     expect(page).to have_css("table tr", count: 2)
   end
-end
+end
\ No newline at end of file
diff --git a/spec/features/distribution_spec.rb b/spec/features/distribution_spec.rb
index 422342321e..2f647f0bee 100644
--- a/spec/features/distribution_spec.rb
+++ b/spec/features/distribution_spec.rb
@@ -61,11 +61,13 @@
     end
 
     context "when one of the items has been 'deleted'" do
-      scenario "the user can still reclaim it and it reactivates the item" do
+      scenario "the user can still reclaim it and it reactivates the item", js: true do
         item = distribution.line_items.first.item
         item.destroy
         expect do
-          click_on "Reclaim"
+          accept_confirm do
+            click_on "Reclaim"
+          end
           page.find ".alert"
         end.to change { Distribution.count }.by(-1).and change { Item.count }.by(1)
         expect(page).to have_content "reclaimed"
@@ -139,13 +141,14 @@
         expect(page).to have_content 13
       end
 
-      scenario "User creates a distribution from a donation then tries to make the quantity too big" do
+      scenario "User creates a distribution from a donation then tries to make the quantity too big", js: true do
         within "#edit_distribution_#{@distribution.to_param}" do
           first(".numeric").set 999_999
           click_on "Save"
         end
         expect(page).to have_no_content "Distribution updated!"
-        expect(page).to have_content "Distribution could not be updated!"
+        # NOTE: This is rendering the app/views/errors/insufficient.html.erb template
+        expect(page).to have_content(/Insufficient/i)
         expect(page).to have_no_content 999_999
         expect(Distribution.first.line_items.count).to eq 1
       end
diff --git a/spec/features/item_spec.rb b/spec/features/item_spec.rb
index 7339992039..3b9f86ab68 100644
--- a/spec/features/item_spec.rb
+++ b/spec/features/item_spec.rb
@@ -88,8 +88,8 @@
     let(:donation_tampons) { create(:donation, :with_items, storage_location: storage, item_quantity: num_tampons_in_donation, item: item_tampons) }
     let(:donation_aux_tampons) { create(:donation, :with_items, storage_location: aux_storage, item_quantity: num_tampons_second_donation, item: item_tampons) }
     before do
-      storage.intake!(donation_tampons)
-      aux_storage.intake!(donation_aux_tampons)
+      storage.increase_inventory(donation_tampons)
+      aux_storage.increase_inventory(donation_aux_tampons)
       visit url_prefix + "/items"
     end
     # Consolidated these into one to reduce the setup/teardown
diff --git a/spec/models/adjustment_spec.rb b/spec/models/adjustment_spec.rb
index 827712179d..9e407f8912 100644
--- a/spec/models/adjustment_spec.rb
+++ b/spec/models/adjustment_spec.rb
@@ -38,6 +38,58 @@
       create(:adjustment, storage_location: storage_location4, organization: storage_location4.organization)
       expect(Adjustment.storage_locations_adjusted_for(@organization).to_a).to match_array([storage_location1, storage_location2])
     end
+
+    describe "split_difference" do
+      it "returns two adjustment objects" do
+        item = create(:item)
+        storage_location = create(:storage_location, :with_items, item: item, item_quantity: 10)
+        storage_location.inventory_items << create(:inventory_item, item: create(:item), quantity: 10)
+        adjustment = create(:adjustment,
+                            storage_location: storage_location,
+                            line_items_attributes: [
+                              { item_id: storage_location.items.first.id, quantity: 10 },
+                              { item_id: storage_location.items.last.id, quantity: -5 }
+                            ])
+        pos, neg = adjustment.split_difference
+        expect(pos.line_items.size).to eq(1)
+        expect(neg.line_items.size).to eq(1)
+        expect(pos.line_items.first.quantity).to eq(10)
+        expect(neg.line_items.first.quantity).to eq(5)
+      end
+
+      it "gracefully handles adjustments with only positive" do
+        item = create(:item)
+        storage_location = create(:storage_location, :with_items, item: item, item_quantity: 10)
+        storage_location.inventory_items << create(:inventory_item, item: create(:item), quantity: 10)
+        adjustment = create(:adjustment,
+                            storage_location: storage_location,
+                            line_items_attributes: [
+                              { item_id: storage_location.items.first.id, quantity: 10 },
+                              { item_id: storage_location.items.last.id, quantity: 5 }
+                            ])
+        pos, neg = adjustment.split_difference
+        expect(pos.line_items.size).to eq(2)
+        expect(pos.line_items.first.quantity).to eq(10)
+        expect(pos.line_items.last.quantity).to eq(5)
+        expect(neg.line_items).to be_empty
+      end
+      it "gracefully handles adjustments with only negative" do
+        item = create(:item)
+        storage_location = create(:storage_location, :with_items, item: item, item_quantity: 10)
+        storage_location.inventory_items << create(:inventory_item, item: create(:item), quantity: 10)
+        adjustment = create(:adjustment,
+                            storage_location: storage_location,
+                            line_items_attributes: [
+                              { item_id: storage_location.items.first.id, quantity: -10 },
+                              { item_id: storage_location.items.last.id, quantity: -5 }
+                            ])
+        pos, neg = adjustment.split_difference
+        expect(neg.line_items.size).to eq(2)
+        expect(neg.line_items.first.quantity).to eq(10)
+        expect(neg.line_items.last.quantity).to eq(5)
+        expect(pos.line_items).to be_empty
+      end
+    end
   end
 
   describe "nested line item attributes" do
diff --git a/spec/models/distribution_spec.rb b/spec/models/distribution_spec.rb
index 53168261cf..e166ed342c 100644
--- a/spec/models/distribution_spec.rb
+++ b/spec/models/distribution_spec.rb
@@ -101,5 +101,16 @@
         expect(distribution.line_items.first.quantity).to eq 15
       end
     end
+
+    describe "#replace_distribution!" do
+      subject { create(:distribution, :with_items, item_quantity: 10) }
+      let(:attributes) { { line_items_attributes: { "0": { item_id: subject.line_items.first.item_id, quantity: 2 } } } }
+
+      it "replaces a big distribution with a smaller one, resulting in increased stored quantities" do
+        expect do
+          subject.replace_distribution!(attributes)
+        end.to change { subject.storage_location.size }.by(8)
+      end
+    end
   end
 end
diff --git a/spec/models/donation_spec.rb b/spec/models/donation_spec.rb
index 42643ce3f5..05405bfee7 100644
--- a/spec/models/donation_spec.rb
+++ b/spec/models/donation_spec.rb
@@ -97,61 +97,14 @@
     describe "items >" do
       it "has_many" do
         donation = create(:donation)
-        item = create(:item)
-        # Using donation.track because it marshalls the HMT
-        donation.track(item, 1)
+        line_item = create(:line_item)
+        donation.line_items << line_item
         expect(donation.items.count).to eq(1)
       end
     end
   end
 
   context "Methods >" do
-    describe "track" do
-      let!(:donation) { create(:donation) }
-      let!(:item) { create(:item) }
-
-      it "does not add a new line_item unnecessarily, updating existing line_item instead" do
-        item = create :item
-        donation.track(item, 5)
-        expect do
-          donation.track(item, 10)
-          donation.reload
-        end.not_to change { donation.line_items.count }
-
-        expect(donation.line_items.first.quantity).to eq(15)
-      end
-    end
-
-    describe "contains_item_id?" do
-      it "returns true if the item_id already exists" do
-        donation = create(:donation, :with_items)
-        expect(donation.contains_item_id?(donation.items.last.id)).to be_truthy
-      end
-    end
-
-    describe "update_quantity" do
-      let!(:donation) { create(:donation, :with_items) }
-      it "adds an additional quantity to the existing line_item" do
-        expect do
-          donation.update_quantity(1, donation.items.first)
-          donation.reload
-        end.to change { donation.line_items.first.quantity }.by(1)
-      end
-
-      it "can receive a negative quantity to subtract inventory" do
-        expect do
-          donation.update_quantity(-1, donation.items.first)
-        end.to change { donation.total_quantity }.by(-1)
-      end
-
-      it "works whether you give it an item or an id" do
-        expect do
-          donation.update_quantity(1, donation.items.first.id)
-          donation.reload
-        end.to change { donation.line_items.first.quantity }.by(1)
-      end
-    end
-
     describe "remove" do
       let!(:donation) { create(:donation, :with_items) }
 
@@ -173,21 +126,53 @@
       end
     end
 
-    describe "remove_inventory" do
-      it "removes inventory from the right storage location when donation is destroyed" do
-        donation = create(:donation, :with_items)
-        expect do
-          donation.destroy
-        end.to change { donation.storage_location.size }.by(-donation.total_quantity)
-      end
-    end
-
     describe "money_raised" do
       it "tracks the money raised in a donation" do
         donation = create(:donation, :with_items, money_raised: 100)
         expect(donation.money_raised).to eq(100)
       end
     end
+
+    describe "replace_increase!" do
+      let!(:storage_location) { create(:storage_location, :with_items, item_quantity: 5, organization: @organization) }
+      subject { create(:donation, :with_items, organization: @organization, item_quantity: 5, storage_location: storage_location) }
+
+      context "changing the donation" do
+        let(:attributes) { { line_items_attributes: { "0": { item_id: subject.line_items.first.item_id, quantity: 2 } } } }
+
+        it "updates the quantity of items" do
+          expect do
+            subject.replace_increase!(attributes)
+            storage_location.reload
+          end.to change { storage_location.size }.by(-3)
+        end
+      end
+
+      context "when adding an item that has been previously deleted" do
+        let!(:inactive_item) { create(:item, active: false) }
+        let(:attributes) { { line_items_attributes: { "0": { item_id: inactive_item.to_param, quantity: 10 } } } }
+
+        it "re-creates the item" do
+          expect do
+            subject.replace_increase!(attributes)
+            storage_location.reload
+          end.to change { storage_location.size }.by(5) # We had 5 items of a different kind before, now we have 10
+                                                 .and change { Item.count }.by(1)
+        end
+      end
+
+      context "with empty line_items" do
+        let(:attributes) { { line_items_attributes: {} } }
+
+        it "removes the inventory item if the item's removal results in a 0 count" do
+          expect do
+            subject.replace_increase!(attributes)
+            storage_location.reload
+          end.to change { storage_location.inventory_items.size }.by(-1)
+                                                                 .and change { InventoryItem.count }.by(-1)
+        end
+      end
+    end
   end
 
   describe "SOURCES" do
diff --git a/spec/models/item_spec.rb b/spec/models/item_spec.rb
index 2966e70918..b63b29bb9d 100644
--- a/spec/models/item_spec.rb
+++ b/spec/models/item_spec.rb
@@ -143,29 +143,25 @@
         expect(item).not_to be_active
       end
     end
-  end
 
-  # context "Callbacks >" do
-  #   describe "when DIAPER_PARTNER_URL is present" do
-  #     let(:diaper_partner_url) { "http://diaper.partner.io" }
-  #     let(:callback_url) { "#{diaper_partner_url}/items" }
-  #
-  #     before do
-  #       stub_env "DIAPER_PARTNER_URL", diaper_partner_url
-  #       stub_env "DIAPER_PARTNER_SECRET_KEY", "secretkey123"
-  #       stub_request :post, callback_url
-  #     end
-  #
-  #     it "notifies the Diaper Partner app" do
-  #       item = create :item
-  #       headers = {
-  #         "Authorization" => /APIAuth diaperbase:.*/,
-  #         "Content-Type" => "application/x-www-form-urlencoded"
-  #       }
-  #       body = URI.encode_www_form item.attributes
-  #       expect(WebMock).to have_requested(:post, callback_url)
-  #         .with(headers: headers, body: body).once
-  #     end
-  #   end
-  # end
+    describe "#reactivate!" do
+      context "given an array of item ids" do
+        let(:item_array) { create_list(:item, 2, :inactive).collect(&:id) }
+        it "sets the active trait to true for all of them" do
+          expect do
+            Item.reactivate(item_array)
+          end.to change { Item.active.size }.by(item_array.size)
+        end
+      end
+
+      context "given a single item id" do
+        let(:item_id) { create(:item).id }
+        it "sets the active trait to true for that item" do
+          expect do
+            Item.reactivate(item_id)
+          end.to change { Item.active.size }.by(1)
+        end
+      end
+    end
+  end
 end
diff --git a/spec/models/purchase_spec.rb b/spec/models/purchase_spec.rb
index d2442d01f7..4ae67c0095 100644
--- a/spec/models/purchase_spec.rb
+++ b/spec/models/purchase_spec.rb
@@ -70,61 +70,14 @@
     describe "items >" do
       it "has_many" do
         purchase = create(:purchase)
-        item = create(:item)
-        # Using purchase.track because it marshalls the HMT
-        purchase.track(item, 1)
+        line_item = create(:line_item)
+        purchase.line_items << line_item
         expect(purchase.items.count).to eq(1)
       end
     end
   end
 
   context "Methods >" do
-    describe "track" do
-      let!(:purchase) { create(:purchase) }
-      let!(:item) { create(:item) }
-
-      it "does not add a new line_item unnecessarily, updating existing line_item instead" do
-        item = create :item
-        purchase.track(item, 5)
-        expect do
-          purchase.track(item, 10)
-          purchase.reload
-        end.not_to change { purchase.line_items.count }
-
-        expect(purchase.line_items.first.quantity).to eq(15)
-      end
-    end
-
-    describe "contains_item_id?" do
-      it "returns true if the item_id already exists" do
-        purchase = create(:purchase, :with_items)
-        expect(purchase.contains_item_id?(purchase.items.first.id)).to be_truthy
-      end
-    end
-
-    describe "update_quantity" do
-      let!(:purchase) { create(:purchase, :with_items) }
-      it "adds an additional quantity to the existing line_item" do
-        expect do
-          purchase.update_quantity(1, purchase.items.first)
-          purchase.reload
-        end.to change { purchase.line_items.first.quantity }.by(1)
-      end
-
-      it "can receive a negative quantity to subtract inventory" do
-        expect do
-          purchase.update_quantity(-1, purchase.items.first)
-        end.to change { purchase.total_quantity }.by(-1)
-      end
-
-      it "works whether you give it an item or an id" do
-        expect do
-          purchase.update_quantity(1, purchase.items.first.id)
-          purchase.reload
-        end.to change { purchase.line_items.first.quantity }.by(1)
-      end
-    end
-
     describe "remove" do
       let!(:purchase) { create(:purchase, :with_items) }
 
@@ -143,12 +96,37 @@
       end
     end
 
-    describe "remove_inventory" do
-      it "removes inventory from the right storage location when purchase deleted" do
-        purchase = create(:purchase, :with_items)
+    describe "replace_increase!" do
+      let!(:storage_location) { create(:storage_location, :with_items, item_quantity: 5, organization: @organization) }
+      subject { create(:purchase, :with_items, item_quantity: 5, storage_location: storage_location, organization: @organization) }
+
+      it "updates the quantity of items" do
+        attributes = { line_items_attributes: { "0": { item_id: subject.line_items.first.item_id, quantity: 2 } } }
+        expect do
+          subject.replace_increase!(attributes)
+          storage_location.reload
+        end.to change { storage_location.size }.by(-3)
+      end
+
+      it "removes the inventory item if the item's removal results in a 0 count" do
+        attributes = { line_items_attributes: {} }
         expect do
-          purchase.remove_inventory
-        end.to change { purchase.storage_location.size }.by(-purchase.total_quantity)
+          subject.replace_increase!(attributes)
+          storage_location.reload
+        end.to change { storage_location.inventory_items.size }.by(-1)
+                                                               .and change { InventoryItem.count }.by(-1)
+      end
+
+      context "when adding an item that has been previously deleted" do
+        let!(:inactive_item) { create(:item, active: false, organization: @organization) }
+        let(:attributes) { { line_items_attributes: { "0": { item_id: inactive_item.id, quantity: 10 } } } }
+        it "re-creates the item" do
+          expect do
+            subject.replace_increase!(attributes)
+            storage_location.reload
+          end.to change { storage_location.size }.by(5)
+                                                 .and change { Item.count }.by(1)
+        end
       end
     end
   end
diff --git a/spec/models/storage_location_spec.rb b/spec/models/storage_location_spec.rb
index 9ff8c96f0d..9f281a6392 100644
--- a/spec/models/storage_location_spec.rb
+++ b/spec/models/storage_location_spec.rb
@@ -13,8 +13,6 @@
 #
 
 RSpec.describe StorageLocation, type: :model do
-  let(:organization) { create(:organization) }
-
   context "Validations >" do
     it "requires a name" do
       expect(build(:storage_location, name: nil)).not_to be_valid
@@ -37,6 +35,78 @@
   end
 
   context "Methods >" do
+    let!(:item) { create(:item) }
+    subject { create(:storage_location, :with_items, item_quantity: 10, item: item, organization: @organization) }
+
+    describe "increase_inventory" do
+      context "With existing inventory" do
+        let(:donation) { create(:donation, :with_items, item_quantity: 66, organization: @organization) }
+
+        it "increases inventory quantities from an itemizable object" do
+          expect do
+            subject.increase_inventory(donation.to_a)
+          end.to change { subject.size }.by(66)
+        end
+      end
+
+      context "when providing a new item that does not yet exist" do
+        let(:mystery_item) { create(:item, organization: @organization) }
+        let(:donation_with_new_items) { create(:donation, :with_items, organization: @organization, item_quantity: 10, item: mystery_item) }
+
+        it "creates those new inventory items in the storage location" do
+          expect do
+            subject.increase_inventory(donation_with_new_items.to_a)
+          end.to change { subject.inventory_items.count }.by(1)
+        end
+      end
+
+      context "when increasing with an inactive item" do
+        let(:inactive_item) { create(:item, active: false, organization: @organization) }
+        let(:donation_with_inactive_item) { create(:donation, :with_items, organization: @organization, item_quantity: 10, item: inactive_item) }
+
+        it "re-activates the item as part of the creation process" do
+          expect do
+            subject.increase_inventory(donation_with_inactive_item.to_a)
+          end.to change { subject.inventory_items.count }.by(1)
+                                                         .and change { Item.count }.by(1)
+        end
+      end
+    end
+
+    describe "decrease_inventory" do
+      let(:item) { create(:item) }
+      let(:distribution) { create(:distribution, :with_items, item: item, item_quantity: 66) }
+
+      it "decreases inventory quantities from an itemizable object" do
+        storage_location = create(:storage_location, :with_items, item_quantity: 100, item: item, organization: @organization)
+        expect do
+          storage_location.decrease_inventory(distribution.to_a)
+        end.to change { storage_location.size }.by(-66)
+      end
+
+      context "when there is insufficient inventory available" do
+        let(:distribution_but_too_much) { create(:distribution, :with_items, item: item, item_quantity: 9001) }
+
+        it "gives informative errors" do
+          storage_location = create(:storage_location, :with_items, item_quantity: 10, item: item, organization: @organization)
+          expect do
+            storage_location.decrease_inventory(distribution_but_too_much.to_a).errors
+          end.to raise_error(Errors::InsufficientAllotment)
+        end
+
+        it "does not change inventory quantities if there is an error" do
+          storage_location = create(:storage_location, :with_items, item_quantity: 10, item: item, organization: @organization)
+          starting_size = storage_location.size
+          begin
+            storage_location.decrease_inventory(distribution.to_a)
+          rescue Errors::InsufficientAllotment
+          end
+          storage_location.reload
+          expect(storage_location.size).to eq(starting_size)
+        end
+      end
+    end
+
     describe "StorageLocation.item_total" do
       it "gathers the final total of a single item across all inventories" do
         item = create(:item)
@@ -75,131 +145,13 @@
       end
     end
 
-    describe "intake!" do
-      it "adds items to a storage location even if none exist" do
-        storage_location = create(:storage_location)
-        donation = create(:donation, :with_items, item_quantity: 10)
-        expect do
-          storage_location.intake!(donation)
-          storage_location.items.reload
-        end.to change { storage_location.items.count }.by(1)
-        expect(storage_location.size).to eq(10)
-      end
-
-      it "adds items to the storage location total if that item already exists in inventory" do
-        storage_location = create(:storage_location, :with_items, item_quantity: 10)
-        donation = create(:donation, :with_items, item_quantity: 10, item: storage_location.inventory_items.first.item)
-        storage_location.intake!(donation)
-
-        expect(storage_location.inventory_items.count).to eq(1)
-        expect(storage_location.inventory_items.where(item_id: donation.line_items.first.item).first.quantity).to eq(20)
-      end
-    end
-
-    describe "remove!" do
-      let(:storage_location) { create(:storage_location) }
-      let(:donation)         { create(:donation, :with_items, item_quantity: 10) }
-
-      before(:each) do
-        storage_location.intake!(donation)
-        storage_location.items.reload
-
-        expect(storage_location.size).to eq(10)
-        expect(storage_location.items.count).to eq(1)
-      end
-
-      it "removes items from a storage location" do
-        expect do
-          storage_location.remove!(donation)
-        end.to change { storage_location.size }.by(-donation.total_quantity)
-                                               .and change { storage_location.inventory_items.size }.by(-donation.line_items.count)
-                                                                                                    .and change { InventoryItem.count }.by(-donation.line_items.count)
-      end
-    end
-
-    describe "adjust_from_past!" do
-      let(:storage_location) { create(:storage_location) }
-      let(:purchase)         { create(:purchase, :with_items, item_quantity: 10) }
-      let(:donation)         { create(:donation, :with_items, item_quantity: 10) }
-
-      context "with_donations" do
-        before(:each) do
-          storage_location.intake!(donation)
-        end
-
-        it "updates the quantity of items" do
-          previous_quantities = donation.line_items_quantities
-          donation.line_items.first.update(quantity: 5)
-          expect do
-            storage_location.adjust_from_past!(donation, previous_quantities)
-            storage_location.reload
-          end.to change { storage_location.size }.by(-5)
-        end
-
-        it "removes the inventory item from the DB if the item's removal results in a 0 count" do
-          previous_quantities = donation.line_items_quantities
-          donation.line_items.first.update(quantity: 0)
-
-          expect do
-            storage_location.adjust_from_past!(donation, previous_quantities)
-            storage_location.reload
-          end.to change { storage_location.inventory_items.size }.by(-1)
-                                                                 .and change { InventoryItem.count }.by(-1)
-        end
-      end
-      context "With purchases" do
-        before(:each) do
-          storage_location.intake!(purchase)
-          storage_location.items.reload
-        end
-
-        it "removes the inventory item from the DB if the item's removal results in a 0 count" do
-          previous_quantities = purchase.line_items_quantities
-          purchase.line_items.first.update(quantity: 0)
-
-          expect do
-            storage_location.adjust_from_past!(purchase, previous_quantities)
-            storage_location.reload
-          end.to change { storage_location.inventory_items.size }.by(-1)
-                                                                 .and change { InventoryItem.count }.by(-1)
-        end
-      end
-    end
-
-    describe "distribute!" do
-      it "distrbutes items from storage location" do
-        storage_location = create :storage_location, :with_items, item_quantity: 300
-        distribution = build :distribution, :with_items, storage_location: storage_location, item_quantity: 50
-        storage_location.distribute!(distribution)
-        expect(storage_location.inventory_items.first.quantity).to eq 250
-      end
-
-      it "raises error when distribution exceeds storage location inventory" do
-        storage_location = create :storage_location, :with_items, item_quantity: 300
-        distribution = build :distribution, :with_items, storage_location: storage_location, item_quantity: 350
-        item = distribution.line_items.first.item
-        expect do
-          storage_location.distribute!(distribution)
-        end.to raise_error do |error|
-          expect(error).to be_a Errors::InsufficientAllotment
-          expect(error.insufficient_items).to include(
-            item_id: item.id,
-            item_name: item.name,
-            quantity_on_hand: 300,
-            quantity_requested: 350
-          )
-        end
-      end
-    end
-
     describe "import_csv" do
       it "imports storage locations from a csv file" do
-        organization
         before_import = StorageLocation.count
         import_file_path = Rails.root.join("spec", "fixtures", "storage_locations.csv")
         data = File.read(import_file_path, encoding: "BOM|UTF-8")
         csv = CSV.parse(data, headers: true)
-        StorageLocation.import_csv(csv, organization.id)
+        StorageLocation.import_csv(csv, @organization.id)
         expect(StorageLocation.count).to eq before_import + 1
       end
     end
@@ -207,88 +159,14 @@
     describe "import_inventory" do
       it "imports storage locations from a csv file" do
         donations_count = Donation.count
-        organization
-        storage_location = create(:storage_location, organization_id: organization.id)
+        storage_location = create(:storage_location, organization_id: @organization.id)
         import_file_path = Rails.root.join("spec", "fixtures", "inventory.csv").read
-        StorageLocation.import_inventory(import_file_path, organization.id, storage_location.id)
+        StorageLocation.import_inventory(import_file_path, @organization.id, storage_location.id)
         expect(storage_location.size).to eq 14_842
         expect(donations_count).to eq Donation.count
       end
     end
 
-    describe "adjust!" do
-      it "combines line item quantities with inventory amounts" do
-        storage_location = create :storage_location, :with_items, item_quantity: 300
-        adjustment = build :adjustment, :with_items, storage_location: storage_location, item_quantity: 50
-        storage_location.adjust!(adjustment)
-        expect(storage_location.inventory_items.first.quantity).to eq 350
-
-        adjustment2 = build :adjustment, :with_items, storage_location: storage_location, item_quantity: -50
-        storage_location.adjust!(adjustment2)
-        expect(storage_location.inventory_items.first.quantity).to eq 300
-      end
-      it "ensures that a user cannot adjust an inventory into the negative" do
-        storage_location = create :storage_location, :with_items, item_quantity: 300
-        adjustment = build :adjustment, :with_items, storage_location: storage_location, item_quantity: -301
-        expect do
-          storage_location.adjust!(adjustment)
-        end.to raise_error(Errors::InsufficientAllotment)
-      end
-    end
-
-    describe "move_inventory!" do
-      it "removes inventory from a storage location and adds them to another storage location" do
-        item = create(:item)
-        storage_location = create :storage_location, :with_items, item: item, item_quantity: 300
-        storage_location2 = create :storage_location, :with_items, item: item, item_quantity: 100
-        transfer = build :transfer, :with_items, item: item, item_quantity: 100,
-                                                 from: storage_location, to: storage_location2
-        storage_location.move_inventory!(transfer)
-        expect(storage_location.inventory_items.first.quantity).to eq 200
-        expect(storage_location2.inventory_items.first.quantity).to eq 200
-      end
-
-      it "raises error when distribution exceeds inventory in a storage facility" do
-        item = create(:item)
-        storage_location = create :storage_location, :with_items, item: item, item_quantity: 100
-        storage_location2 = create :storage_location, :with_items, item: item, item_quantity: 100
-        transfer = build :transfer, :with_items, item: item, item_quantity: 200,
-                                                 from_id: storage_location.id, to_id: storage_location2.id
-        expect do
-          storage_location.move_inventory!(transfer)
-        end.to raise_error(Errors::InsufficientAllotment)
-      end
-    end
-
-    describe "reclaim!" do
-      it "adds distribution items back to storage location" do
-        storage_location = create :storage_location, :with_items, item_quantity: 300
-        distribution = create :distribution, :with_items, storage_location: storage_location, item_quantity: 50
-        storage_location.reclaim!(distribution)
-        expect(storage_location.inventory_items.first.quantity).to eq 350
-      end
-
-      it "re-activates items that were previously deleted" do
-        storage_location = create :storage_location, :with_items, item_quantity: 200
-        distribution = create :distribution, :with_items, storage_location: storage_location, item_quantity: 50
-        item = distribution.line_items.first.item
-        expect do
-          item.destroy
-        end.to change { item.active }.from(true).to(false)
-        expect do
-          storage_location.reclaim!(distribution)
-          item.reload
-        end.to change { item.active }.from(false).to(true)
-      end
-
-      it "does not destroy the distribution" do
-        storage_location = create :storage_location, :with_items, item_quantity: 300
-        distribution = create :distribution, :with_items, storage_location: storage_location, item_quantity: 50
-        storage_location.reclaim!(distribution)
-        expect(Distribution.find(distribution.id)).to eql distribution
-      end
-    end
-
     describe "geocode" do
       it "adds coordinates to the database" do
         storage_location = build(:storage_location,
diff --git a/spec/support/itemizable_shared_example.rb b/spec/support/itemizable_shared_example.rb
index f9c827271f..67613582d1 100644
--- a/spec/support/itemizable_shared_example.rb
+++ b/spec/support/itemizable_shared_example.rb
@@ -97,20 +97,5 @@
         end.to change { subject.line_items.total }.by(10)
       end
     end
-
-    describe "updated line item quantity" do
-      subject { create(model_f, organization: @organization) }
-      let(:storage_location) { subject.storage_location }
-
-      it "updates storage location quantity by the correct amount" do
-        line_item = subject.line_items.create(item_id: item.id, quantity: 10)
-        inventory_item = create(:inventory_item, storage_location: storage_location, item_id: line_item.item_id)
-        previous_quantities = subject.line_items_quantities
-        line_item.update!(quantity: 5)
-        expect do
-          storage_location.adjust_from_past!(subject, previous_quantities)
-        end.to change { inventory_item.reload.quantity }.by(-5)
-      end
-    end
   end
 end
diff --git a/spec/system/adjustment_system_spec.rb b/spec/system/adjustment_system_spec.rb
index cac3f1ddec..88f3331a19 100644
--- a/spec/system/adjustment_system_spec.rb
+++ b/spec/system/adjustment_system_spec.rb
@@ -17,7 +17,7 @@
     expect do
       click_button "Save"
     end.to change { storage_location.size }.by(add_quantity)
-    expect(page).to have_content("Adjustment was successfully created")
+    expect(page).to have_content(/Adjustment was successful/i)
   end
 
   it "can subtract an inventory adjustment at a storage location", js: true do
@@ -33,7 +33,7 @@
     expect do
       click_button "Save"
     end.to change { storage_location.size }.by(sub_quantity)
-    expect(page).to have_content("Adjustment was successfully created")
+    expect(page).to have_content(/Adjustment was successful/i)
   end
 
   it "can filter the #index by storage location" do
diff --git a/spec/system/transfer_system_spec.rb b/spec/system/transfer_system_spec.rb
index 6994649028..c3126afb95 100644
--- a/spec/system/transfer_system_spec.rb
+++ b/spec/system/transfer_system_spec.rb
@@ -17,7 +17,26 @@
       fill_in "transfer_line_items_attributes_0_quantity", with: "10"
       click_on "Save"
     end
-    expect(page).to have_content("Transfer was successfully created")
+    expect(page).to have_content("10 items have been transferred")
+  end
+
+  context "when there's insufficient inventory at the origin to cover the move" do
+    let!(:from_storage_location) { create(:storage_location, :with_items, item_quantity: 10, name: "From me", organization: @organization) }
+    let!(:to_storage_location) { create(:storage_location, :with_items, name: "To me", organization: @organization) }
+
+    scenario "User can transfer an inventory from a storage location to another" do
+      visit url_prefix + "/transfers"
+      click_link "New Transfer"
+      within "form#new_transfer" do
+        select from_storage_location.name, from: "From storage location"
+        select to_storage_location.name, from: "To storage location"
+        fill_in "Comment", with: "something"
+        select from_storage_location.items.first.name, from: "transfer_line_items_attributes_0_item_id"
+        fill_in "transfer_line_items_attributes_0_quantity", with: "100"
+        click_on "Save"
+      end
+      expect(page).to have_content("exceed the available inventory")
+    end
   end
 
   it "can filter the #index by storage location both from and to as a user" do